POS0492 ASSESSMENT OF OSTEOPOROSIS AND VERTEBRAL FRACTURE RISK BY OPPORTUNISTIC BONE MINERAL DENSITY (BMD) MEASUREMENT ON CHOLINE PET/CT IN PATIENTS WITH PROSTATE CANCER (HORM-OS PROJECT)
Authors: A. Dauchez, C. Dariane, J. Fechtenbaum, S. Bodard, S. Guinebert, F. Allioux, M. O. Timsit, C. Roux, F. Hyafil, K. Briot, O. Fogel
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Androgen deprivation therapy (ADT) is central in the management of advanced prostate cancer (PCa) but is associated with bone loss and occurrence of osteoporosis and fracture. Dual-energy x-ray absorptiometry (DXA) is recommended when starting ADT but is rarely done. Opportunistic measurement of bone mineral density (BMD) on CT has been proposed to improve osteoporosis screening in the general population, but has not been evaluated in PCa. Choline PET/CT (chPET/CT) is frequently used to identify the recurrence of PCa and/or search for metastasis. <h3>Objectives</h3> The objectives were to demonstrate the feasibility of using chPET/CT in comparison to the CT scan for opportunistic screening of osteoporosis and to describe the pet/ct-derived BMD and the prevalence of osteoporotic vertebral fracture in patients with PCa. <h3>Methods</h3> Between 2020 and 2022, we identified 171 PET/CT from 136 patients in the database of the nuclear medicine department of our tertiary center. We focused on chPET/CT. Among these patients, we identified those with a CT within 6 months before or after the chPET/CT to compare the BMD values between these 2 exams. BMD estimation was performed by 4 blinded readers (2 rheumatologists and 2 radiologists) on a 200-mm² trabecular bone area by a standardized method, on L1 vertebrae in axial section. Assessment of vertebral fractures and metastasis was performed on the entire spine in sagittal section. Demographic, clinical and treatments information have been collected blind from the reading of the images. Spearman coefficient and t-test were used for continuous variables and chi square test was used for dichotomous variables. <h3>Results</h3> We identified 93 PCa patients with chPET-CT including 29 with a CT within 6 months. The mean age was 74 years old (± 8.6), and mean BMI was 26.9 kg/m² (± 5.2). Forty-one patients (44%) smoked or had smoked. ChPET/CT was performed for newly-diagnosed PCa in 36.6%, for suspicion of recurrence in 59.1% or as simple follow-up for 4.3%. Twelve patients (12.9%) had fractures and 20 (21.5%) had metastasis. Also, 39 patients (42%) were already on ADT with a mean duration of 21.4 ± 31.6 months. First, we compared BMD measurement on both chPET/CT and CT in the 29 patients. The mean BMD on L1 vertebrae was similar between the 2 exams (125 ± 51.1 and 128 ± 42.4 HU respectively on chPET-CT and CT) and correlated well (k = 0.7; p &lt; 0.001). Then, we measured the pet/ct-derived BMD on the whole cohort. The mean BMD was 125 HU (± 50.7). Increasing age was significantly correlated with decreased BMD (k = -0.315; p &lt; 0.001). There was no correlation between BMI and BMD (k = 0.02; p = 0.87). The mean BMD was 123 HU (± 51.6) in patients who smoked or had smoked, compared with 138 HU (± 45.8) in non-smokers (p = 0.11). The mean BMD in patients already on ADT was 114 HU (± 56.2), compared with 127 HU (± 42.1) in others (p = 0.17). Among the 39 patients on ADT, there was a nonsignificant trend toward decreased BMD with increased ADT duration (k = -0.27; p = 0.1). Interestingly we found a significant decreased BMD for patients with fracture compared to those without fracture (mean BMD = 82.6 ± 42.9 vs 131 ± 49; p &lt; 0.01). A cut-off of 100 HU has recently been published on CT to define patients at risk for bone complications. Here, we identified 24.7% patients with a BMD &lt; 100 HU. These patients were more likely to have vertebral fracture compared to those with a BMD &gt; 100 HU (30.4% vs 7.1% of fracture; p &lt; 0.01). <h3>Conclusion</h3> This study demonstrates the feasibility of using chPET-CT for opportunistic screening for osteoporosis in PCa. Bone disease was frequent in this population, 13% patients had fractures and almost 25% had a BMD &lt; 100 HU. Pet/ct-BMD seemed to be of interest for screening patients at risk of fracture. A prospective study will validate the interest of this approach and its impact on the management of osteoporosis in these patients. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.